In general, a small-sized camera module is mounted in a mobile terminal such as a smartphone. In such a camera module, a lens driving device is employed (for example, PTLS 1 and 2). The lens driving device has an auto focus function of automatically performing focusing for capturing a subject (hereinafter referred to as “AF (Auto Focus) function”), and a shake correction function (hereinafter referred to as “OIS (Optical Image Stabilization) function”) of optically correcting shake (vibration) upon capturing an image to reduce the irregularities of the image.
The auto-focusing and shake-correcting lens driving device includes an auto-focusing driving part (hereinafter referred to as “AF driving part”) for moving the lens part in the light axis direction, and a shake-correcting driving part (hereinafter referred to as “OIS driving part”) for swaying the lens part in a plane orthogonal to the light axis direction.
The AF driving part includes, for example, an auto-focusing coil part (hereinafter referred to as “AF coil part”) disposed around the lens part, and an auto-focusing magnet part (hereinafter referred to as “AF magnet part”) disposed separately from the AF coil part in the radial direction. An auto-focusing movable part (hereinafter referred to as “AF movable part”) including the lens part and the AF coil part is moved with respect to an auto-focusing fixing part (hereinafter referred to as “AF fixing part”) including the AF magnet part in the light axis direction by use of a driving force of a voice coil motor composed of the AF coil part and the AF magnet part, and thus focusing is automatically performed.
Here, a lens position for bringing a subject at a smallest capture distance (a position on the most light reception side) into focus is called “macro position,” and a lens position for bringing a subject at the infinity (a position on the most imaging side) into focus is called “infinity position.” That is, the range from the macro position to the infinity position is the movable range of the AF movable part.
The OIS driving part includes a shake-correcting magnet part (hereinafter referred to as “OIS magnet part”) disposed at the AF driving part, and a shake-correcting coil part (hereinafter referred to as “OIS coil part”) disposed separately from the OIS magnet part in the light axis direction, for example. A shake-correcting movable part (hereinafter referred to as “OIS movable part”) including the AF driving part and the OIS magnet part is supported by a supporting member so as to be separated from a shake-correcting fixing part (hereinafter referred to as “OIS fixing part”) including the OIS coil part in the light axis direction. The OIS movable part is swayed in a plane orthogonal to the light axis direction by use of a driving force of a voice coil motor composed of the OIS magnet part and the OIS coil part, and thus shake correction is performed.
FIGS. 1A and 1B illustrate a displacement width of a lens part in a conventional lens driving device. FIG. 1A illustrates a neutral (non-energization) state, and FIG. 1B illustrates a state at the time of dropping. In FIGS. 1A and 1B, the OIS magnet part serves also as the AF magnet part.
In the lens driving device illustrated in FIGS. 1A and 1B, AF movable part 11 where a lens part is disposed includes lens holder 111 and AF coil part 112, and AF fixing part 12 includes magnet holder 121 and magnet part 122 (AF magnet part). In addition, OIS movable part 10 includes an AF driving part (AF movable part 11 and AF fixing part 12), and is supported in a state where it is separated from OIS fixing part 20 including an OIS coil part (not illustrated) on the light reception side in the light axis direction.
In FIGS. 1A and 1B, AF movable part 11 moves to the imaging side or the light reception side in the light axis direction to perform focusing. AF movable part 11 can move to the imaging side in the light axis direction by L1 (hereinafter referred to as “lower movable range L1”). In addition, OIS movable part 10 is separated from OIS fixing part 20 by L2 (hereinafter referred to as “magnet gap L2”) for swaying in a plane orthogonal to the light axis direction.
Accordingly, when an impact of dropping or the like is applied to the lens part, the lens part is displaced by up to a movable distance (L1+L2) of AF movable part 11 to the imaging side in the light axis direction. When the distance L3 between the lens part and the image capturing part is greater than the maximum displacement (L1+L2) of the lens part, collision with the image capturing part is not caused even when the lens part is displaced to the imaging side in the light axis direction by an impact of dropping or the like.